yep nice WP theme.
you can make it better changing the background image some what like your targeted content. but withe same color scheme. if you want to stay with WP.
in WP put a clickable direct link to the forum on side bar or on the top pages links. adding to the top would be a nice idea but with that you'll have to put a statement in that new page to redirect it to the forum. if dont want to make this trouble just you can put it as a link on side bar.
but as you have other pages with your own content. on that point wampyr is right.
but if you have some idea tricking with WP you can manage to take your all pages in it as I have seen in your above links.
and if you are not familier with WP development, then really keep away from it
and your own black layout, try to use frames very less, or use them carefully as you are not taking the real advantage of frames currently.
and in tab buttons use transparent gif images rather than with white corners.
and put this tab line right above the frame below without any space.